The Rough-toothed Dolphin is a tropical to subtropical species, which generally inhabits deep, oceanic waters of all three major oceans, rarely ranging north of 40°N or south of 35°S (Jefferson 2002). However, in some areas (such as off the coast of Brazil and West Africa), rough-toothed dolphins may occur in more shallow coastal waters. They are found in many semi-enclosed bodies of water (such as the Gulf of Thailand, Red Sea, Gulf of Mexico, Caribbean Sea, and Gulf of California), but they are regarded as visitors in the Mediterranean Sea (Watkins et al. 1987, Miyazaki and Perrin 1994, Reeves and Notarbartolo di Sciara 2006).

The map shows where the species may occur based on oceanography. The species has not been recorded for all the states within the hypothetical range as shown on the map. States for which confirmed records of the species exist are included in the list of native range states. States within the hypothetical range but for which no confirmed records exist are included in the Presence Uncertain list.

There are few estimates of abundance for this species. An estimated 145,900 (CV=32%) Rough-toothed Dolphins inhabit the eastern tropical Pacific (Wade and Gerrodette 1993), and about 2,746 (CV=36%) occur in the northern Gulf of Mexico (Waring et al. 2008), including an estimated 1,238 (CV=65%) on the continental shelf (Fulling et al. 2003). The US NMFS has estimated the regional population around Hawaii to be 19,904 (CV=52%), based on recent vessel surveys (Carretta et al. 2006).

Most often, Steno bredanensis is found in deep water far offshore, usually beyond the continental shelf (Maigret 1994), but may be seen close inshore in areas of steep bottom relief (Ritter 2002). In the eastern tropical Pacific, they tend to associate with other cetaceans (especially pilot whales and Fraser’s dolphins) (Miyazaki and Perrin 1994). Rough-toothed Dolphins feed on cephalopods and fish, including large fish such as Coryphaena hippurus (Pitman and Stinchcomb 2002).

No fisheries are known to specifically target this species, but small numbers are taken in drive fisheries at Okinawa in the Ryukyus and other islands of Japan, the Solomon Islands and Papua New Guinea, by harpoon in Japan, St. Vincent in the Lesser Antilles, and in West Africa. They were possibly formerly were taken at St. Helena in the South Atlantic. However, only 23 Rough-toothed Dolphins were captured in Japan (Okinawa) during the period 1976-81 (Miyazaki and Perrin 1994). Recent information suggests catches in Taiwan (J. Wang pers. comm.).

A few Rough-toothed Dolphins are killed incidentally in tuna purse seines in the eastern tropical Pacific: 21 were estimated killed during the period 1971-75 and 36 died in a single net haul in 1982. Small numbers are also taken as by-catch in gillnet and driftnet fisheries in Sri Lanka, Brazil, the central North Pacific and probably elsewhere around the world in tropical and warm-temperate waters (Miyazaki and Perrin 1994). Monteiro-Neto et al. (2000) reported on fishery-related mortality along the coast of Ceara State, northeast Brazil, commenting on the possible conservation implications for the local subpopulations. Seasonally, incidental catches were more frequent during the austral spring (October-December). Rough-toothed Dolphins are also taken by gill nets, driftnets and pelagic long-lines in Taiwan (J. Wang pers. comm.).

In-Place Research, Monitoring and PlanningIn-Place Land/Water Protection and ManagementIn-Place Species ManagementIn-Place Education Included in international legislation:Yes Subject to any international management/trade controls:Yes